A useful function within a computer application or program. (noun)
The capacity of a computer program or application to provide a useful function. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "functionality" in a sentence
"The Garmin functionality is cool, but I didn't like the actual watch - I've gone for a Suunto T1c, and am enjoying it enough to wear as a regular watch fairly often."
"Right now our main functionality is centered around the News Popularity Index and managing channels by reputation."
"Let's now remove the label functionality, and build a separate decorator for that."